Certain bag systems may include a collecting bag intended to receive the blood taken from a donor and intended for transfusion to another person, and a sampling bag intended to receive the first millilitres of blood taken. Both bags are generally flexible, and are formed, for example, from two sheets connected to each other near their periphery.
A first tube is connected at a first end to a collection means, such as a phlebotomy needle intended to be inserted into the arm of the donor, and at a second end to an inlet orifice of the collecting bag.
A second tube is connected at one end to the first tube and at the other end to an inlet orifice of the sampling bag.
A closure system, such as a clamp, is placed on each of the two tubes and makes it possible to direct the blood donated to the sampling bag or to the collecting bag.
A lateral sampling device, connected outside the sampling bag to the second tube, enables the blood contained in the sampling bag to be withdrawn by means of vacuum tubes. The samples of blood thus obtained are normally systematically analysed in order to determine the rhesus group, to make a count and to detect any contaminations such as viruses, bacteria or other undesirable elements present in the blood of the donor, before transfusing the blood to another person.
Filling the sampling bag prior to the collecting bag presents a certain number of advantages and improves the quality of the samples and the blood remaining for transfusion.
First, this reduces the risk of contamination of the blood intended for transfusion. Such contamination often results from the presence of bacteria or other foreign substances on the skin of the donor. However, the first millilitres of blood taken, which are most likely to exhibit these foreign substances, are sent into the sampling bag rather than into the collecting bag, thereby greatly decreasing the chances of contamination of blood in the collecting bag.
Second, this arrangement makes it possible to take samples before the collecting bag is completely filled, and consequently save time.
Finally, during donation, the loss of blood volume for the donor may be compensated for by plasma. As a result, the hematocrit of the donor blood may appear artificially lower if samples are taken after the collection bag is filled.
Although this system has proven very beneficial, room for improvement remains. In one such previous system, the end part of the second tube is inserted in the inlet orifice of the sampling bag but does not enter inside the bag, or it enters only a short distance.
This presents several drawbacks due to the fact that, when the sampling bag is placed so that its inlet orifice is situated towards the top, the end of the second tube connected to the said inlet orifice is situated above the blood-air interface.
Thus, in the event of unintentional pressure on the sampling bag, the latter deforms because of its flexibility, and as a result part of the air contained in this bag rises in the tube. Because the sampling bag is connected to the collection means, there is a not insignificant risk of gas embolism, that is to say entry of air into the venous system of the donor. Additionally, it is known that an entry of air upstream of the heart may cause drainage of the heart pump and cardio-circulatory arrest, which may sometimes lead to death of the donor.
Even in the absence of unintentional pressure on the sampling bag, this configuration is not entirely satisfactory because the failure of the second tube to be immersed in the blood contained in the sampling bag (when the bag is in the aforementioned position) renders it impossible to fill tubes for analysis of the blood in the sampling bag while that bag is being filled. Instead, once the sampling bag is filled, it must be turned over so that the inlet orifice is situated downwards before samples may be removed by vacuum tube. This causes an undesired loss of time.
In another example of the previous sampling bag/collecting bag system, the end part of the second tube is inserted in the inlet orifice of the sampling bag and enters inside the bag, so that the corresponding end of the second tube is situated in the immediate vicinity of the bottom of the bag. This is in particular described in U.S. Pat. No. 6,387,086. However, this arrangement is also not fully satisfactory.
Specifically, when the bag is oriented so that the end of the tube is situated downwards, the end is in contact with the blood rather than with air very soon after blood begins to enter the sampling bag, and the embolism problems encountered with the first embodiment may be avoided. However, it is desirable to be able to place and use the sampling bag in an inverted position, where the inlet orifice is situated not towards the top but towards the bottom. This places the end of the second tube above the blood and may allow air to enter it. In this case, the system of the document U.S. Pat. No. 6,387,086 poses the same problems as those described above for the embodiment in which the second tube does not enter the sampling bag.
Moreover, in this version of the sampling bag system, the longer the end part of the second tube situated inside the sampling bag, the greater the volume of air contained in the said bag, before any collection of blood for sampling. Specifically, the volume of air is the sum of:                the volume contained in the end part of the second tube situated inside the sampling bag; and        the volume of air trapped around the second tube, over its entire length, between the two sheets forming the sampling bag.        
Thus, the greater the length of the end part of the second tube inserted inside the bag, the greater the volume of air available to rise up in the tube as far as the vein of the donor. The risk of gas embolism is considerably increased thereby.
It is therefore particularly important to ensure that the volume of air contained inside the bag before blood donation is initiated is limited to the maximum possible extent. This is particularly true when air from a tube, such as the second tube, will be added to volume of air in the sampling bag after blood donation begins.